Tandem concrete mixer



July 31, 1951 w. o. FROHRING TANDEM CONCRETE MIXER Filed ma 5, 1950 FIG-I F IG.

F I 6- 2 INVENTOR. WII LIAM O. FROHRI NG ATTORNEYS Patented July 31, 1951 UNITED. STATE TANDEM CONCRETE MIXER William O. Frohring, N ewbury Township,

Geauga County, Ohio 7 Application May 5, 1950, Serial No. 160,290

1 Claim. 1

The invention relates to novel and improved concrete mixing apparatus. An object of the invention is to provide means of this general type for increasing efficiency and decreasing labor and apparatus costs in the production of mixtures of concrete and the like, particularly in non-commercial installations such as in the home or farm.

Other objects and advantages will be apparent from a study of the following'specification, in conjunction with the'accompanying drawings, in which Fig. 1 is a side eleva'tional view of a tandem concrete mixer embodying my invention;

Fig. 2 is an end elevational view as seen from the left of Fig. 1; and

Fig. 3 is a sectional view taken on the line 3-3 of Fig. 1.

As .will appear, the apparatus now to be described consists of two concrete mixing bowls operatively linked to a single driving power source, but otherwise capable of independent operation, so that while one bowl is being rotated for mixing the concrete, the other bowl is being loaded or unloaded. In this way exceptionally high operating efficiency can be attained.

The mixing apparatus includes a pair of frame supports l5 and it upon which are respectively supported a pair of mixing bowls ii and I8 which are adapted to tilt in parallel vertical planes about a common horizontal axis I4 (Fig. 2). The bowls are of conventional conical bell type having at one end respective loading openings l9 and which of course also serve as discharge openings. Each bowl is carried and operated in a similar manner so that, for the time being, the structure of one only will be described.

Bowl 18 is supported on a rotatable yoke 23 having opposed stub shafts 24 and 25 journaled in frame l6. Stub shaft 24 is axially pierced to accommodate a drive shaft 2| (Fig. 3) provided at its inner end with a driving bevel pinion 2! in mesh with an annular bevel gear 29 secured to the bowl periphery, whereby rotation of shaft 2| rotates pinion 21, and bowl [8.

Stub shaft 25 is fixed to swing with yoke 23, and may be integral therewith, and has affixed. to its outer end an operatin handle or crank 30 whereby the yoke and bowl are tiltable back and forth in a plane at right angles to the driving axis through shafts 24 and 25.

Bowl I! has a similar operating crank 33 on the outer end of its stub shaft 34, and its inner stub shaft 35 has a similar driving linkage and pinion. The driving shafts 2| and 22 are con,- nected through universal joint linkage 3'! to pro vide for a limited amount of misalignment of the said shafts. A drivin pulley 28 is fixed to drive shaft 22.

A. 'moments consideration will make it ap: parent that with a driving linkage such as shown and described, the bowls will rotate in opposite directions, and this fact must be taken into ac: count in providing for proper orientation of the agitating vanes or mixing vanes in the bowl interiors.) p

I have schematically illustrated driving means 39 connected by means of a V-belt All with pulley 28. Driving means 39 can be a' small gasoline motor such as is frequently used for utility purposes in homes or on farms. Anelectric motor could of course be used, although electric current is not always'available on farms.

The operation of the device in a'preferred cycle is as follows. I

The bowls are preferably loaded on one side of the apparatus, and unloaded on the other side. Said sides will be hereinafter designated respectively as the loading side (left side, Fig. 2) and the unloading side (right side, Fig. 2), it being understood that the loading side for both bowls is the same. At the beginning of an operation both bowls may point in the same direction or may be inclined as shown in Fig. 2, but one only is first loaded, for example, bowl it). When it is loaded, and while it is in material retaining position, the mixing operation proceeds. During such operation the operator still on the loading side tilts bowl H to the loading side and loads it.

By the time bowl I1 is loaded, and is in the early stage of mixing, bowl I8 is ready to be discharged, and the operator tilts it over to the unloading side by means of crank 30. It may be dumped into a wheelbarrow or other suitable receptable, and bowl I8 is then tilted back towards the loading side and loaded. By the time this loading of bowl I8 is completed, bowl ll will be ready to be discharged. Continuance of the successive cycles will be apparent from what has just been said.

The advantages of this structure, and the mode of operation which it permits, are as follows.

Two bowls arranged in tamdem and being charged alternately, and discharged alternately, and each undergoin a mixing operation while the other is being discharged and then charged, afiords a much more efficient operation than would a single large bowl of double the capacity of either small bowl. With the small bowls, one

is mixing while the other is being discharged and charged, while with one large bowl no eflicient operation is being performed while the mixing operation is going forward.

Assume for example that the production of two bowls, each of 3 cu. ft. capacity, linked and operated as hereinabove described, is to be compared for eificiency with the operation of one bowl of 6 cu. ft. capacity. Assume that it takes an operator 5 minutes to load a 3 cu. ft. bowl, and 5 minutes to discharge it. Assume that a minute period is acceptable for mixing. Under these assumptions, 3 cubic feet of cement will be poured every 10 minutes, or 9 cubic feet in 30 minutes.

Now if an operator needs 5 minutes to load a 3 cu. ft. bowl it will take him 10 minutes to load a 6 cu. ft. bowl, and another 10 minutes to discharge it. In addition there will be a 10 minute mixing period. Therefore in 30 minutes, only 6 cubic feet of cement is poured, as compared with 9 cubic feet when operating two small bowls. This is a fifty per cent increase in efficiency in favor of the small bowls, although the total potential capacity is the same.

Further, my arrangement permits the use of a single driving means for both bowls, instead of two such means when the bowls are not linked as shown and described. This effects a material saving in cost,

The equipment I have shown and described can handle a small job, say only 3 cubic feet, without resorting to tandem operation. Either at the universal joint, or elsewhere, the two mixers may be disconnected for independent usage of only one bowl.

If two operators are used, one operator can handle charging while the other operator discharges, each one of course alternating from one bowl to the other. In this way a practically continuous flow of concrete is obtained.

The particular arrangement I have shown, in which both mixers are connected in tandem to rotate in opposite directions, permits the disposing of the tilting controls on the outside of the machines, away from the motor, which makes it both safe and convenient for the operator.

What I claim is:

Mixing apparatus of the character described comprising a supporting frame, a pair of mixing bowls spaced and journaled on respective stub shafts in said frame, the axes of said shafts being in substantial alignment whereby said bowls are tiltable in parallel planes around and perpendicular to said axes, means for rotating each said bowl around an axis of rotation coincident with said respective planes, driving linkage means extending between said bowls and engaging, at its opposed ends, with said means for rotating said bowls, single driving power means operatively linked to said driving linkage means whereby both bowls can be simultaneously rotated from said driving power means, each bowl being provided with independent operator-operatable tilting means for tilting either bowl independently of the other.

WILLIAM O. FROHRING.

REFERENCES CITED The following references are of record in the file of this patent:

UNITED STATES PATENTS Number Name Date 1,314,390 French Aug. 26, 1919 2,482,324 Dachkevitch Sept. 20, 1949 FOREIGN PATENTS Number Country Date 563,600 Germany Nov. 9, 1932 

